1. Field of the Invention
The present invention relates to a substrates processing device for supplying process solution such as resist and developer solutions to the surface of each of objects to be processed such as semiconductor wafers.
2. Description of the Related Art
According to the conventional devices for coating each of the semiconductor wafers with photo-resist solution, resist film is formed on each of the semiconductor wafers in such a way that the semiconductor wafer to be processed is sucked and held on a rotatable spin chuck, that resist solution which serves as process solution is dropped onto the rotating semiconductor wafer through a resist supply nozzle located above the spin chuck, that resist solution is spread all over the wafer by centrifugal force caused when the spin chuck is rotated at low speed, and that resist solution is shaken off from the wafer and dried while rotating the spin chuck at high speed.
The supply of resist solution to the resist supply nozzle is achieved through a resist supply pipe which includes a solution level detecting sensor, a pressure pump, a filter and a valve. In short, resist solution in a resist bottle is fed every certain amount to the nozzle by the pressure pump, while detecting the top level of resist solution in the bottle by the sensor. Particles caused in the pressure pump and others are removed from resist solution this time when resist solution passes through the filter. This prevents particles from being supplied to the semiconductor wafer. The valve is a combination of a switching valve and a suck-back valve and the suck-back valve serves to suck resist solution remaining in the nozzle not to be mistakenly dropped onto the surface of the semiconductor wafer through the nozzle when the switching valve is closed to stop the supply of resist solution to the nozzle.
This coating solution supply mechanism is a must for both of those coating devices which are of the solution-dropping and -spraying types.
In the case of the above-described coating solution supply mechanism used for the above-mentioned coating devices, however, solution is supplied to the resist supply nozzle by the pressure pump. This makes it unavoidable for particles and bubbles to enter into coating solution such as resist solution.
In addition, the pressure pump, the filter and the like must be attached to the supply pipe. This makes it necessary to provide fittings between the supply pipe and the pressure pump and between the supply pipe and others. Solution leakage is thus caused through those portions of the supply pipe to which these fittings are attached. This is quite troublesome. Further, it takes a lot of effort and a long time to attach the fittings to the supply pipe not to cause any solution leakage. Still further, resist solution is stayed in those stepped portions and clearances which are formed inside the fittings of the supply pipe in the case of the resist coating device, for example. Resist solution thus stayed is changed into gel as time goes by and these gel-like particles enter into resist solution.
On the other hand, there has been provided a coating device wherein coating solution is not fed by the pump but it is pressure-fed by inactive gas such as nitrogen gas. In the case of this coating device, however, the bottle in which coating solution such as resist solution is contained must be kept pressurized at all times. This is quite dangerous.